West Pacific/2015/11W/Archive/1
Public advisory TROPICAL STORM NANGKA PUBLIC ADVISORY NUMBER 1 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST SAT JUL 04 2015 ...DISTURBANCE WITHIN THE MARSHALL ISLANDS DEVELOPS INTO NANGKA... SUMMARY OF 12:00 AM JST...15:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...9.5N, 170.4E CENTER POSITION CONFIDENCE: HIGH ... ± 20 MI... 30 KM ABOUT 850 MI...1,370 KM ENE OF PALIKIR, MICRONESIA MAXIMUM SUSTAINED WINDS...35 KT...40 MPH...65 KM/H MINIMUM BAROMETRIC PRESSURE...1002 MB...29.60 INCHES PRESENT MOVEMENT...WNW AT 13 KT...15 MPH...24 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 12:00 am JST, the center of Tropical Storm Nangka was situated near 9.5N, 170.4E, or about 855 miles (1,370 kilometers) east-northeast of Palikir, Micronesia. Maximum sustained winds were 35 knots (40 mph, 65 km/h), with higher gusts. The minimum barometric pressure was 1002 millibars (hPa; 29.60 inHg), and the cyclone was tracking west-northwest 13 knots (15 mph, 24 km/h). Conditions are expected to be generally favorable for slow intensification of the next few days as Nangka tracks generally west-northwestward throughout the forecast period. NEXT ADVISORY ------------------- Next complete advisory at 06:00 am JST. $$ Forecaster TheAustinMan Discussion TROPICAL STORM NANGKA PUBLIC ADVISORY NUMBER 1 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST SAT JUL 04 2015 The area of disturbed weather within the Marshall Islands has steadily organized over the past few hours. Conventional satellite animations indicate that deep convection has increased in both aerial coverage and intensity, while an early morning Rapidscat pass depicted the formation of a better defined and closed low-level circulation. The pass also indicated a small area of 35kt winds in the northeastern quadrant of the system, and thus advisories are being initiated on Tropical Storm Nangka at this time. However, given the presentation of the cyclone, it would not be surprising if this value were conservative. The intensity forecast for Nangka is somewhat complicated. Maps from UW-CIMSS indicate that the upper-level pattern is currently characterized by anticyclonic flow, yielding 5 to 15 knots of shear over the cyclone. These values would favor slow to steady development over the coming days, as indicated by the GFS. However, the ECMWF on the other hand does not show much change in strength over the coming days, with a majority of the intensification occurring outside the forecast period. Examining forecast maps at 200mb, it appears that the upper-level environment could become less-than-ideal after 36 hours, both a result of upper-level outflow from Chan-hom and an upper-level trough to the system's northwest imparting moderate northerly shear. As such, the WHFC forecast is less bullish than the GFS, which shows Nangka becoming a typhoon by 48 hours, but more bullish than the ECMWF, which keeps the system below typhoon intensity throughout the forecast period. It should be noted that Nangka is a small cyclone–it is susceptible to rapid changes in intensity, both upward and downward. Nangka is currently moving on a swift west-northwest trajectory, steered by an expansive 594dm ridge to the system's north. This steering mechanism is expected to maintain dominance for most of the forecast period. By 120 hours, however, the cyclone is expected to approach the western periphery of the feature and begin to track more poleward. This is reflected by the GFS and ECMWF well, and the WHFC track forecast closely follows suit. On its current path, Nangka is expected to pose a threat to the central and northern Mariana Islands, and residents there should monitor the progress of the system closely. INIT 03/1500Z 9.5N 170.4E 35 KT 40 MPH 12H 04/0000Z 9.9N 169.5E 40 KT 45 MPH 24H 04/1200Z 10.2N 168.1E 45 KT 50 MPH 36H 05/0000Z 10.6N 165.8E 50 KT 60 MPH 48H 05/1200Z 11.0N 163.0E 50 KT 60 MPH 72H 06/1200Z 11.4N 158.2E 55 KT 65 MPH 96H 07/1200Z 13.6N 153.9E 55 KT 65 MPH 120H 08/1200Z 16.8N 149.2E 65 KT 75 MPH $$ Forecaster TAWX14